ASA 127th Meeting M.I.T. 1994 June 6-10

2aSA10. Response of a pseudo-periodically ribbed shell to a point drive.

Douglas Photiadis

Brian Houston

Earl Williams

Joseph Bucaro

NRL, Code 7131, 4555 Overlook Ave. SW, Washington, DC 20375-5000

Near periodic arrays of discontinuities have been predicted to have a
significant impact on the acoustic properties of elastic structures. Recent
experimental results obtained at the Naval Research Laboratory have
demonstrated the importance of the multiple scattering of flexural waves on the
acoustic far field, but the surface propagation characteristics of such
structures are still uncertain. Near-field pressure measurements of the
response of an irregularly ribbed cylindrical shell to a point drive have now
been performed. Using near-field acoustic holography (NAH), the surface
velocity field of the structure is reconstructed, and further data analysis,
modal and wave-number decomposition, is performed. The dispersion relations and
the associated apparent damping factors for the propagating waves on the
structure are hence experimentally determined. These results and interpretation
of the data will be presented.